Thermally insulative smoking article filter components

ABSTRACT

A filter component includes a catalyst surrounded by a thermally insulative carbon fiber composite. The catalyst can catalyze the chemical reaction of selected gaseous constituents of a gas stream. During catalysis, the catalyst can reach high temperatures. The carbon fiber composite can contain heat generated during the catalysis within the filter component and thereby reduce heat transfer to the surroundings. The filter component can be used in smoking articles. Methods of making and using the filter-component and methods for treating mainstream tobacco smoke are also provided.

BACKGROUND

A catalyst is a substance that can accelerate the rate of certainchemical reactions, but without being consumed or undergoing a chemicalchange itself.

Chemical reactions that occur with the evolution of heat to thesurroundings are called exothermic reactions, and have a negativeenthalpy change, i.e., ΔH<0. Chemical reactions that occur with theabsorption of heat from the surroundings are called endothermicreactions, and have a positive enthalpy change, i.e., ΔH>0.

SUMMARY

Smoking article filters useful for catalyzing the chemical reaction ofone or more selected constituents of mainstream tobacco smoke areprovided. In a preferred embodiment, the filter comprises a filtercomponent, which includes a porous carbon-bonded carbon fiber compositecontaining a catalyst. The catalyst is preferably located in one or morehollow spaces provided in the carbon fiber composite, and/or distributedthroughout the carbon fiber composite. The catalyst provided in thecomposite is effective to cause catalytic conversion via reaction of atleast one constituent of mainstream tobacco smoke to an innocuous gas,e.g., the chemical reaction of carbon monoxide to carbon dioxide.

In another preferred embodiment, the carbon fiber composite is amonolithic body without a cavity and the catalyst is contained withinthe body of the carbon fiber composite.

The carbon fiber composite is a thermal insulator and has low thermalconductivity. The carbon fiber composite can contain heat evolved duringthe chemical reaction(s) within the filter component. By containing thisheat, the catalyst can remain at an elevated temperature within thecarbon fiber composite to enhance its catalytic performance. The carbonfiber composite preferably can also prevent excessive heat from reachingother portions of the filter that are sensitive to such heat.

In a preferred embodiment, the filter includes a flavoring-releaseadditive, which includes flavoring disposed downstream from the carbonfiber composite. The flavoring-release additive can have a selectedminimum flavoring-release temperature. Heat that is evolved during oneor more chemical reactions catalyzed by the catalyst can be transferredto the flavoring-release additive via the mainstream smoke and utilizedto heat the flavoring-release additive to at least the minimumflavoring-release temperature, thereby causing release of the flavoringin the filter.

A preferred embodiment of a method of making a filter comprisesincorporating into a filter component including a carbon fiber compositea catalyst effective to catalyze the chemical reaction of at least oneselected gaseous constituent of mainstream smoke.

A preferred embodiment of a method of making a cigarette comprisesplacing a paper wrapper around a tobacco column to form a tobaccocolumn, and attaching a cigarette filter to the tobacco column to formthe cigarette. The cigarette filter includes a filter component having aporous carbon-bonded carbon fiber composite containing a catalyst thatcan catalyze the chemical reaction of at least one selected gaseousconstituent of mainstream smoke passing through the filter. The filtercomponent can optionally also include a flavoring-release additive.

A preferred embodiment of a method of treating mainstream tobacco smokecomprises heating or lighting a cigarette to form smoke, and drawing thesmoke through the cigarette such that the catalyst contained in thecarbon fiber composite catalyzes the chemical reaction of at least oneselected gaseous constituent of mainstream smoke. The cigarette can be atraditional or a less-traditional cigarette, such as a cigarette of anelectrical heated cigarette smoking system or a cigarette that containsa combustible heat source.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1A depicts an embodiment of a carbon-bonded carbon fiber compositeincluding two open ends closed by covers.

FIG. 1B is an enlarged view of catalyst material contained in thecarbon-bonded carbon fiber composite shown in FIG. 1A.

FIG. 2 depicts another embodiment of the carbon-bonded carbon fibercomposite including a single open end and cover.

FIG. 3 depicts another embodiment of a carbon-bonded carbon fibercomposite including a single open end closed by an alternative coverconfiguration.

FIG. 4 is a photomicrograph showing a carbon-bonded carbon fibercomposite produced from rayon fibers.

FIG. 5 is a photomicrograph showing a carbon-bonded carbon fibercomposite produced from pitch fibers having a length of about 100 μm.

FIG. 6 is a photomicrograph showing a carbon-bonded carbon fibercomposite produced from poly(acrylonitrile) (PAN) fibers.

FIG. 7 is a photomicrograph showing a carbon-bonded carbon fibercomposite produced from pitch fibers having a length of 200 μm.

FIG. 8 is a longitudinal cross-sectional view of a carbon-bonded carbonfiber composite including a body, covers and carbon fibers lyingsubstantially in parallel planes along the longitudinal axis A-A of thecomposite.

FIG. 9 is a photomicrograph of a carbon fiber composite including carbonfibers lying substantially in planes parallel to the longitudinal axis.

FIG. 10 is a longitudinal cross-sectional view of another embodiment ofa carbon-bonded carbon fiber composite including carbon fibers lyingsubstantially in planes extending orthogonal to the longitudinal axisA-A of the composite.

FIG. 11 is photomicrograph of another preferred embodiment of acarbon-bonded carbon fiber composite, which includes carbon fibers lyingsubstantially in planes orthogonal to the longitudinal axis of thecomposite.

FIG. 12 is a transverse cross-sectional view of another preferredembodiment of the carbon-bonded carbon fiber composite includingcircumferentially-oriented carbon fibers.

FIG. 13 depicts another preferred embodiment of the carbon-bonded carbonfiber composite having a monolithic structure and including carbonfibers extending along the longitudinal axis of the composite.

FIG. 14 depicts another preferred embodiment of the carbon-bonded carbonfiber composite having a monolithic structure and including carbonfibers extending orthogonal to the longitudinal axis of the composite.

FIG. 15 shows the thermal conductivity versus density for fourcarbon-bonded carbon fiber composites respectively including differenttypes of carbon fibers which extend along the longitudinal axis of thecomposite (i.e., “in-plane”), and for four carbon-bonded carbon fibercomposites also respectively including different types of carbon fibers,but which extend orthogonal to the longitudinal axis of the composite(i.e., “out-of-plane”).

FIG. 16 depicts the maximum compressive stress applied before failurefor carbon fiber composites including carbon fibers having lengths ofabout 100 μm (pitch fibers), about 150 μm (PAN fibers), about 200 μm(pitch fibers) and about 380 μm (rayon fibers), where the carbon fibersare oriented either “in-plane” or “out-of-plane.”

FIG. 17 depicts the thermal conductivity versus carbon fiber length forcarbon fiber composites including carbon fibers having lengths of about100 μm (pitch fibers), about 150 μm (PAN fibers), about 200 μm (pitchfibers) and about 380 μm (rayon fibers), where the carbon fibers areoriented either “in-plane” or “out-of-plane.”

FIG. 18 depicts the thermal conductivity ratio, i.e., the ratio of thein-plane thermal conductivity to the out-of-plane thermal conductivity,for carbon fiber composites including carbon fibers having lengths ofabout 100 μm (pitch fibers), about 150 μm (PAN fibers), about 200 μm(pitch fibers) and about 380 μm (rayon fibers), where the carbon fibersare oriented either “in-plane” or “out-of-plane.”

FIG. 19 depicts the change with respect to time of (a) the CO content ofgas passed through a tubular, porous, carbon-bonded carbon-fibercomposite containing Co-based oxide catalyst material, and (b) theexternal temperature of the composite, as a function of passing N₂-10%O₂—WACO gas through the composite.

FIG. 20 depicts the relationship between the catalyst temperature andthe gas flow rate for N₂-10% O₂—CO gas mixtures having different COcontents flowed through a carbon-bonded carbon fiber composite.

FIG. 21 shows the relationship between the RTD (resistance to draw) andcarbon-bonded carbon fiber composite density for composites includingfour different types of carbon fibers, where the body and the cover ofthe composite both include the same type of carbon fiber.

FIG. 22 shows the relationship between the RTD and carbon-bonded carbonfiber composite density for composites produced using four differenttypes of carbon fibers, where the body and the cover of the compositesinclude different types of carbon fibers.

FIG. 23 illustrates an exemplary cigarette including a tubular filterelement.

FIG. 24 illustrates an exemplary cigarette including a plug-space-plugfilter element.

FIG. 25 illustrates an exemplary cigarette for an electrical smokingsystem.

DETAILED DESCRIPTION

Smoking article filter components are provided that include a thermallyinsulative, porous carbon-bonded carbon fiber composite containingcatalyst material. The catalyst material is effective to catalyze thechemical reaction of at least one gaseous constituent of tobacco smokepassing through the composite.

The chemical reaction(s) that occur in the smoking article can beexothermic and evolve a large quantity of heat. Such chemical reactionscause the temperature of the catalyst to increase significantly in thesmoking article. The carbon-bonded carbon fiber composite is a thermalinsulator that can substantially contain heat that is evolved bychemical reaction(s) that occur within the composite. Consequently,heating of the outer surface of the composite and its surroundings inthe smoking article can be controlled. In addition, because thecomposite is a thermal insulator, the catalyst contained in thecomposite is able to operate in an elevated-temperature environment,which enhances its catalytic performance.

The smoking article filter components are useful for various smokingarticles, e.g., cigarettes, pipes, cigars and non-traditionalcigarettes.

As used herein, the term “sorption” denotes filtration by absorptionand/or adsorption. “Sorption” includes interactions on the outer surfaceof the sorbent, as well as interactions within the pores and channels ofthe sorbent. In other words, a “sorbent” is a substance that cancondense or hold molecules of other substances on its surface, and/ortake up other substances, i.e., through penetration of the othersubstances into its inner structure, or into its pores. As used herein,a “sorbent” refers to an adsorbent, an absorbent, or a substance thatcan perform both of these functions.

As described herein, “mainstream smoke” includes the mixture of gases,solid particles and aerosol that passes down the smoking article andissues through the filter or mouth end, i.e., the smoke that issues oris drawn from the mouth end of a smoking article during smoking.Mainstream smoke includes air that is drawn in through both the litregion of a smoking article, as well as air drawn through the paperwrapper in a cigarette.

FIG. 1A illustrates a preferred embodiment of a filter component 50including a porous, carbon-bonded carbon fiber composite 52. The carbonfiber composite 52 includes a tubular body 54 having an outer surface56, an inner surface 58 defining a cavity 60 and opposed open ends 62,64. Two covers 66, 68 close the respective open ends 62, 64. The covers66, 68 preferably include a portion 72 extending into the cavity 60. Theportion 72 can be sized so that the covers 66, 68 can be press fit ontothe body 54 to close the open ends 62, 64, respectively. As describedbelow, a catalyst material 90 occupies at least a portion of the cavity60, and preferably substantially the entire volume of the cavity 60(i.e., excluding the space between the catalyst particles). FIG. 1B isan enlarged view of the catalyst 90 shown in detail in FIG. 1A.

A filter component 150 according to another preferred embodiment isshown in FIG. 2. The filter component 150 comprises a porous,carbon-bonded carbon fiber composite 152 including a body 154 having anouter surface 156 and an inner surface 158 defining a cavity 160. In theembodiment, the body 154 is tubular and includes a single open end 162and an opposite closed end 165. A cover 166 closes the open end 162.Catalyst material occupies at least a portion of the cavity 160,preferably substantially the entire volume of the cavity 160.

A filter component 250 according to another preferred embodiment isshown in FIG. 3. The filter component 250 comprises a carbon fibercomposite 252 including a body 254 having an outer surface 256, an innersurface 258 defining a cavity 260, an open end 262 and a closed end 265.A cover 266 closes the open end 262. Sufficient catalyst material isprovided to occupy at least a portion of the cavity 260, preferablysubstantially the entire volume of the cavity 260. In an alternativeembodiment, the body 254 can include two open ends and two covers.

The porous, carbon-bonded carbon fiber composite includes carbon fibersinterbonded by a carbonized material and voids between the carbonfibers. The carbon fibers preferably have a length of from about 50 μmto about 400 μm, more preferably from about 50 μm to about 200 μm. Thecarbon fibers preferably have a diameter of from about 10 μm to about 30μm. The carbon fiber composite preferably has a porosity of from about50% to about 95% by volume, more preferably from about 80% to about 90%by volume, and preferably has a density of from about 0.2 g/cm³ to about0.6 g/cm³. The structure of the carbon fiber composite immobilizes thecarbon fibers, while also providing sufficiently high gas permeabilityfor use in a smoking article. The carbon fiber composites can alsoprovide a low thermal conductivity of from about 0.1 W/m·K to about 0.3W/m·K.

Carbon fiber composite structures produced using different interbondedcarbon fiber materials are shown in FIGS. 4-7, each taken at the samemagnification. FIG. 4 shows a carbon fiber composite including rayonfibers having a length of about 380 μm; FIG. 5 shows a carbon fibercomposite including pitch fibers having a length of about 100 μm; FIG. 6shows a carbon fiber composite including poly(acrylonitrile) (PAN)fibers having a length of about 100 μm, and FIG. 7 shows a carbon fibercomposite including pitch fibers having a length of about 200 μm.

The carbon fibers contained in the carbon fiber composite preferablyhave a fiber orientation resulting from the process used to manufacturethe composite. FIG. 8 schematically illustrates a preferred embodimentof a filter component 350 comprising a carbon fiber composite 352including a body 354 having a cavity 360, and covers 366, 368 forclosing opposed open ends of the body 354. The carbon fibers arearranged in planes 380 that lie substantially parallel to thelongitudinal axis A-A of the filter component 350 in the body 354 and inthe covers 366, 368.

The carbon fibers that are used to produce the carbon fiber compositeshave anisotropic thermal conductivity characteristics, i.e., the thermalconductivity of the carbon fiber composite is higher in a directionparallel to the planes of the carbon fibers than in other directions ofthe carbon fiber composite, e.g., in a direction orthogonal to theplanes. Accordingly, in the filter component 350, the thermalconductivity of the carbon fibers is highest in the planes 380 extendingalong the longitudinal axis A-A.

FIG. 9 shows the fiber structure of a carbon fiber composite includingcarbon fibers oriented to extend predominantly along the longitudinalaxis A-A of the filter component, such as in the planes 380 of thefilter component 350 shown in FIG. 8.

Alternatively, the carbon fibers of the carbon fiber composite can havedifferent orientations with respect to the longitudinal axis of thefilter component than the orientation shown in FIG. 8. For example, FIG.10 shows a filter component 450 comprising a porous, carbon-bondedcarbon fiber composite 452, which includes carbon fibers in planes 480extending orthogonal to the longitudinal axis A-A of the filtercomponent in the body 454 and also in the covers 466, 468.

FIG. 11 shows the fiber structure of a carbon fiber composite thatincludes carbon fibers oriented to extend in a direction predominantlyorthogonal to the longitudinal axis A-A of the filter component, such asin the filter component 450 shown in FIG. 10. In the filter component450, the thermal conductivity of the carbon fibers is highest in theplane 480 of the carbon fibers, i.e., in the direction orthogonal to thelongitudinal axis A-A.

FIG. 12 depicts a body 554 and cavity 560 of a porous, carbon-bondedcarbon fiber composite 552 according to another embodiment. The carbonfiber composite 552 includes carbon fibers 580 oriented predominantly inthe circumferential direction of the body 554. This orientation of thecarbon fibers reduces heat conduction in a radial direction of the body554 between the inner surface 558 and the outer surface 556, therebyproviding for a more uniform circumferential temperature distribution onthe outer surface 556 and preferably avoiding “hot spots” on the outersurface 556.

The filter component can have various shapes and sizes. For example, theouter surface of the body of the carbon fiber composite can becylindrical, square, rectangular, of other polygonal shapes, and thelike. The cavity of the body also can have various transversecross-sectional shapes, such as cylindrical, square, rectangular, otherpolygonal shapes and the like.

The body of the carbon fiber composite can include a single cavity, oralternatively two or more cavities. The same or different catalystmaterial can be placed in each cavity. For example, the body can includeone, two, or more cylindrical cavities, each containing catalystmaterial.

The one or more cavities can be located at one or more respectiveselected locations along the length of the body of the carbon fibercomposite. For example, the cavity can be located at the upstream end ofthe body (i.e., the end closer to the tobacco column) and extend alongonly a portion of the length of the body in a cigarette. Placing thecavity at such location can increase the length of the body downstreamof the catalyst and thereby contain heat further away from the mouth endof the cigarette. The carbon fiber composite can also be located closerto the tobacco column to achieve this effect.

The size of the filter component can be appropriately selected based onthe size of the space in the smoking articles in which it is placed. Forexample, when the filter component is used in a filter of a cigarette,the filter component can be cylindrical and have a length preferablyless than about 20 mm, more preferably less than about 15 mm. The outerdiameter of the body and cover(s) of the carbon fiber composite ispreferably slightly less than the diameter of the cigarette. Forexample, the outer diameter of the body and cover(s) of the carbon fibercomposite can be slightly less than about 8 mm, which is a typicalcigarette outer diameter. When the filter component is used in a smokingarticle other than a cigarette, the filter component can have suitabledimensions for those smoking articles. For example, when used in acigar, the filter component preferably has a width or diameter slightlyless than the width or diameter of the cigar.

The one or more cover(s) of the carbon fiber composite preferably have athickness along the longitudinal axis A-A that minimizes the pressuredrop across the cover(s). For example, the cover configurations shown inFIGS. 1-3 preferably have a maximum thickness of less than about 2 mm,more preferably less than about 1 mm. The covers preferably also havesufficient strength to be mounted to the body of the carbon fibercomposite, such as by press fit, bonding, or other suitable mountingtechnique.

The one or more cavities of the carbon fiber composite can beappropriately sized to hold a suitable amount of catalyst material. Forexample, the one or more cavities can be sized to contain a total offrom about 25 mg to about 200 mg of catalyst material, more preferablyfrom about 50 mg to about 150 mg of catalyst material. In an exemplaryembodiment, the body can include a single cylindrical cavity having adiameter of from about 4.5 mm to about 6.5 mm, and a length of fromabout 10 mm to about 20 mm. The catalyst material volume preferablyfills, or at least substantially fills, the one or more cavities inwhich it is contained, so as to reduce settling of the catalyst, butwithout presenting an undesirable increase in the resistance to draw(RTD) when utilized in a smoking article.

However, in other embodiments, the filter component can have aconfiguration that does not include a cavity for containing thecatalyst. For example, FIG. 13 depicts an embodiment of the filtercomponent 650 that has a monolithic structure without a cavity. In theembodiment, the carbon fiber composite 652 includes carbon fibers lyingin planes 680 oriented along the longitudinal axis A-A. This orientationof the planes 680 of the carbon fibers reduces heat transfer from thecarbon fibers to the outer surface 656. Catalyst material can beprovided, e.g., on the carbon fibers, and/or dispersed in voids betweencarbon fibers by, e.g., mechanically or physically impregnating a slurrycontaining catalyst material after forming the filter composite.Covalent chemical attachment can also be used.

In such embodiments, the filter component can include a hollow tube orsleeve fitted over the carbon fiber composite 652, where the sleeve doesnot contain catalyst material so that heat is not generated in thesleeve by chemical reactions catalyzed by catalyst material. The sleevecan provide additional thermal insulation to the filter component.

The monolithic filter component 650 preferably has a sufficiently lowdensity so that it has suitably low resistance to gas flow through thefilter component. The filter component 650 can have various outer shapesand sizes, such as shapes having a round or polygonal outer surface. Thefilter component 650 can be sized based on the size of the space in thesmoking article in which it is used.

FIG. 14 depicts a filter component 750 according to another preferredembodiment. The filter component 750 includes a porous, carbon-bondedcarbon fiber composite 752 having a monolithic structure. Carbon fibersextend in planes 780 oriented orthogonal to the longitudinal axis A-A ofthe filter component 750. The carbon fibers are preferably located toreduce heat transfer from the fibers to the outer surface 756. Catalystmaterial can be provided, e.g., on the carbon fibers and/or dispersedbetween the carbon fibers.

The catalyst material contained in the filter component can have anysuitable composition. The catalyst material can be selected to catalyzethe chemical reaction of one or more selected constituents of a gas. Forexample, the catalyst material preferably is effective to catalyze theoxidation of CO by the following reaction: 2 CO+O₂→2 CO₂. This reactionis strongly exothermic (ΔH=−283 kJ/mole) and thus evolves a largequantity of heat. The catalyst material can also be selected to catalyzeother chemical reactions, such as the reduction of nitric oxide (NO) toN₂.

Suitable catalysts for the oxidation of carbon monoxide include thecobalt-based catalysts described in commonly-assigned U.S. Pat. No.5,502,019, which is incorporated herein by reference in its entirety.The cobalt-based catalyst is preferably a binary oxide catalyst ofcobalt and manganese. The atomic ratio of cobalt to manganese in thecatalyst is preferably from about 15:1 to about 10:1. The cobalt-basedcatalyst can be another cobalt-based binary or higher order oxide, suchas an oxide of cobalt and one or more of the metals Al, Bi, Ce, Cr, Cu,Fe, La, Mg, Ti, Zn and Zr. The cobalt-based catalysts are useful at lowtemperatures to oxidize carbon monoxide, e.g., at room temperature. Thecobalt-based catalysts can be made by methods described in the '019patent.

Other catalysts that can be used in the filter component to oxidizecarbon monoxide, as well as to catalyze other chemical reactions, arethe cerium oxide-copper catalysts described in commonly-assigned U.S.Patent Application Publication No. 2004/0110633, which is incorporatedherein by reference in its entirety. These catalysts can catalyzeoxidation or reduction reactions, such as the oxidation of carbonmonoxide, or reduction of nitric oxide.

Additional catalysts that can be used in the filter component includecatalysts described in commonly-assigned U.S. Patent ApplicationPublication Nos. 2003/0075193, 2003/0131859, 2004/0007241, 2004/0025895,2004/0250654, 2004/0250825, 2004/0250827, and in commonly-assigned U.S.Pat. Nos. 6,769,437 and 6,782,892, each of which is incorporated hereinby reference in its entirety. The catalysts can include metal particlesand/or metal oxide particles including B, Mg, Al, Si, Ti, Fe, Co, Ni,Cu, Zn, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Ce, Hf, Ta, W, Re, Os, Ir,Pt, Au and mixtures thereof.

The catalyst particles can be micron-sized particles, nanoscale-sizedparticles (i.e., have an average particle size less than about 100 nm),or mixtures thereof. Nanoscale particles have a very high surface areato volume ratio, which can enhance their catalytic performance.

The catalyst contained in the cavity of the carbon fiber compositepreferably provides a suitably low resistance to gas flow. In apreferred embodiment, the catalyst is an agglomerate of catalystparticles. For example, the agglomerates can have a size of 14 mesh to20 mesh according to U.S. Standard, ASTM E11 (i.e., a size of 1410 μm to850 μm, respectively). The catalyst particles can be entirely ofcatalyst material, or the catalyst particles can be mixed with and/orsupported on support material, which may enhance catalytic activity bypromoting a favorable orientation or dispersion to increase surfacearea. In an embodiment, the catalyst particles of the agglomerates canhave a size of from about 5 μm to about 30 μm. Such agglomerates havesuitably low resistance to gas flow for use in the filter components.

The catalyst support material can be, e.g., the support materialdescribed in U.S. Patent Application Publication 2004/0250827. Forexample, the catalyst support can comprise inorganic oxide particles,such as silica gel beads, molecular sieves (e.g., zeolites), magnesia,alumina, silica, titania, zirconia, iron oxide, cobalt oxide, nickeloxide, copper oxide, yttria optionally doped with zirconium, manganeseoxide optionally doped with palladium, ceria and mixtures thereof. Also,the catalyst support can comprise activated carbon particles. Thecatalyst support can act as a sorbent and/or be catalytically active inthe filter component.

As described above, it has been determined that the orientation ofcarbon fibers having a length of 100 μm to 400 μm relative to thelongitudinal axis of the carbon fiber composite affects thermalproperties of the carbon fiber composite. FIG. 15 shows the relationshipbetween thermal conductivity and density for carbon fiber compositesmade from four different lengths of the following carbon fibers (i.e.,380 μm rayon, 200 μm pitch, 150 μm PAN, and 100 μm pitch). In four ofthe carbon fiber composites, the carbon fibers extend along thelongitudinal axis A-A of the filter component, as shown in the upper“in-plane” curve. In four other carbon fiber composites, the same carbonfibers extend orthogonal to the longitudinal axis A-A of the filtercomponent, as shown in the lower “out-of-plane” curve. The carbon fibercomposites including the same type of carbon fibers have the same orsimilar density. As shown, the carbon fiber composites including carbonfibers extending along the longitudinal axis each have a higher thermalconductivity along the longitudinal axis than the carbon fibercomposites including carbon fibers of the same material, but which arearranged orthogonal to the longitudinal axis.

The carbon fiber planes in the body and in the cover(s) of the carbonfiber composite can have the same orientation, or a respectivelydifferent orientation, relative to the longitudinal axis. In anexemplary embodiment, the carbon fiber planes in the body and in thecover(s) extend along the longitudinal axis (see FIG. 8). In suchembodiments, the carbon fiber planes of highest thermal conductivityextend parallel to each other in both the body and cover(s). In anotherexemplary embodiment, the carbon fiber planes in the body extend eitheralong the longitudinal axis or orthogonal to the longitudinal axis, withthe carbon fiber planes in the cover(s) extending in the other of thetwo directions. In such embodiments, the planes of highest thermalconductivity in the body and covers are orthogonal to each other.

The lengths of the carbon fibers affects mechanical and thermalproperties of the carbon fiber composite. FIG. 16 depicts the maximumcompressive stress applied to carbon fiber composites before failure ofthe composites. This maximum compressive stress is defined herein as the“compressive strength” of a carbon fiber composite. The carbon fibercomposites that were tested included carbon fibers having lengths ofabout 100 μm (pitch fibers), about 150 μm (PAN fibers), about 200 μm(pitch fibers), and about 380 μm (rayon fibers), where the carbon fibersare oriented either “in-plane” or “out-of-plane.”

As shown, the maximum compressive stress applied to the carbon fibercomposites (or compressive strength) decreased as the carbon fiberlength increased for both the “in-plane” and “out-of-plane” fiberorientations. The highest and lowest measured maximum compressive stressvalues correspond to the shortest and longest carbon fiber lengths,respectively. The average in-plane compressive strength for the carbonfiber composites including 100 μm pitch fibers is about 20 MPa, whichrepresents an increase by a factor of about five compared to the averageout-of-plane compressive strength for the carbon fiber compositesincluding 380 μm rayon fibers, and also an increase in specificcompressive strength (strength/density). For an in-plane carbon fiberorientation, the carbon fiber composite preferably has a compressivestrength of from about 5 MPa to at least about 20 MPa. The averageout-of-plane compressive strength for the carbon fiber compositesincluding 100 μm pitch fibers is about 10 MPa, which represents anincrease by a factor of about eight compared to the average out-of-planecompressive strength for the carbon fiber composites including 380 μmrayon fibers, and also an increase in specific compressive strength(strength/density) by a factor of about four. For an out-of-plane carbonfiber orientation, the carbon fiber composite preferably has acompressive strength of from about 3 MPa to at least about 10 MPa. Byincreasing the strength of the carbon fiber composites by using shorterfibers, the wear resistance, durability and machineability of thecomposites can preferably be improved.

FIG. 17 depicts the thermal conductivity versus carbon fiber length forcarbon fiber composites including carbon fibers having lengths of about100 μm (pitch fibers), about 150 μm (PAN fibers), about 200 μm (pitchfibers), and about 380 μm (rayon fibers), where the carbon fibers areoriented either “in-plane” or “out-of-plane.” As shown, the in-planethermal conductivity of the carbon fiber composites including shortercarbon fibers was increased as compared to the composites includingrayon fibers. The out-of-plane thermal conductivity is increased by theshorter carbon fibers, but only by less than a factor of two.Accordingly, reducing the length of the carbon fibers provides forincreased compressive strength without increasing the thermalconductivity of the carbon fiber composites by an unsuitable amount.

FIG. 18 depicts the thermal conductivity ratio, i.e., the ratio of thein-plane thermal conductivity to the out-of-plane thermal conductivity,for carbon fiber composites including carbon fibers having lengths ofabout 100 μm (pitch fibers), about 150 μm (PAN fibers), about 200 μm(pitch fibers), and about 380 μm (rayon fibers), where the carbon fibersare oriented either “in-plane” or “out-of-plane.” In FIG. 18, thesymbols “A” and “B” designate that the respective measurements were madeby two different sources. As shown, decreasing the carbon fiber lengthof the carbon fiber composites reduces the anisotropy of the thermalconductivity, i.e., it decreases the thermal conductivity ratio.

FIG. 19 represents the variation with respect to time of the CO contentof gas passed through a filter component containing a Co-based oxidecatalyst, and the external temperature of the filter component for aN₂-10% O₂-6% CO gas. The carbon fiber composites include 150 μm PANfibers and closed ends. As shown, at even the high internal temperaturesof the filter component resulting from oxidation of CO catalyzed by thecatalyst, the external temperature of the carbon fiber composite slowlyincreases, and typically reaches a maximum temperature of less thanabout 100° C. after about 2 to 3 minutes of continuous gas flow andapproximately 100% conversion of CO. For the shorter time period ofnormal puffing of a cigarette (i.e., about 2 seconds), externaltemperatures of the filter component are expected to be lower,preferably close to ambient temperature.

Comparative tests were conducted by flowing a CO-containing gas mixturethrough capsules made from Pitch 100, PAN 150 fibers and Pitch 200fibers to determine CO conversion and the external temperature reachedby the capsules. A Co—Mn (10:1) oxide catalyst was made byco-precipitation, sieved to obtain a 0.8-1.4 mm particle size, andcalcined at 250° C. in O₂ for 3 hours. About 140 mg of the catalyst wasinserted into each of the capsules. The catalyst was initially at roomtemperature. The gas mixture contained 10% N₂/6% O₂/6% CO flowing at1.06 Lpm. The gas mixture was flowed through the capsules for 60 secondsand the external temperature of the capsules that was reached after 60seconds was measured using a thermocouple. The percent CO conversion wasalso determined.

The test results are shown in the Table. As shown, a high CO conversionof at least about 97% was achieved for each of the capsules. Theexternal temperatures of the capsules ranged from 64° C. to 71° C.

TABLE Fiber External Capsule Plane CO Temperature Fiber MaterialDirection Conversion (%) After 60 s (° C.) Pitch IN 99.8 64 100 OUT 97.171 PAN IN — — 150 OUT 98.0 67 Pitch IN 96.7 64 200 OUT 99.2 ~66  

FIG. 20 depicts the variation in the catalyst temperature with respectto the gas flow rate and CO content of a N₂-10% O₂—CO gas. The carbonfiber composites include 150 μm PAN fibers and have closed ends. Asshown, increasing the CO content of the gas increases the catalysttemperature at a given gas flow rate. The catalyst reaches a temperatureof about 500° C. at the highest CO content.

FIG. 21 shows the RTD versus carbon fiber composite density for carbonfiber composites made of different carbon fibers. The carbon fibercomposites include a tubular body, two open ends and a cover closingeach open end. The body and the cover both include the same type ofcarbon fiber. Curve “A” represents carbon fiber composites including“in-plane” carbon fibers and also a catalyst; curve “B” representscarbon fiber composites including “in-plane” carbon fibers, but nocatalyst; curve “C” represents carbon fiber composites including“out-of-plane” carbon fibers and also a catalyst; and curve “D”represents carbon fiber composites including “out-of-plane” carbonfibers, but no catalyst. As shown, for a given carbon fiber compositedensity, the RTD values vary between the different carbon fibercomposites.

FIG. 22 shows the resistance to draw versus carbon fiber compositedensity for carbon fiber composites, in which the body includes 100 μmpitch fibers, and the cover includes a different type of carbon fiber.Curve “A” represents carbon fiber composites including “in-plane” carbonfibers and also a catalyst; curve “B” represents carbon fiber compositesincluding “in-plane” carbon fibers, but no catalyst; curve “C”represents carbon fiber composites including “out-of-plane” carbonfibers and also a catalyst; and curve “D” represents carbon fibercomposites including “out-of-plane” carbon fibers, but no catalyst. Asshown, for a given carbon fiber composite density, the RTD values varybetween the different carbon fiber composites.

Comparing the curves in FIGS. 21 and 22, curves C and A in FIG. 22exhibit lower maximum RTD values than those shown in FIG. 21.Accordingly, by arranging the carbon fibers along the longitudinal axisof the filter component in the body and cover(s), the RTD of the filtercomponent can generally be lowered.

In a preferred embodiment, the filter component is oriented to extendlengthwise along the length dimension of a cigarette or other smokingarticle. Such orientation of the filter component increases the lengthof the flow path through the catalyst traversed by mainstream tobaccosmoke, thereby exposing the smoke to an increased catalyst surface area.Accordingly, the catalysis of selected constituents of the mainstreamtobacco smoke by the catalyst can be increased.

However, increasing the length of the filter component can increase thepressure drop along its length corresponding to a given gas flow ratethrough the filter component. Because increasing the pressure drop canincrease the RTD of the smoking article, in preferred embodiments, thelength of the filter component provides for a desirable RTD of thesmoking article.

The carbon fiber composite can be made, e.g., by the method described inGeorge C. Wei and J. M. Robbins, “Carbon-Bonded Carbon Fiber Insulationfor Radioisotope Space Power Systems,” Ceramic Bulletin, vol. 64, no. 5,pp. 691-699 (1985), which is incorporated herein by reference in itsentirety. The method comprises forming a slurry by mixing carbon fiberswith a binder. The slurry can be a water slurry or a non-aqueous slurry.Preferably, water is used to form the slurry because it can be readilyremoved from the slurry by subsequent processing. For example, carbonfibers and binder particles can be combined to form a water slurry,which is subsequently dried and heated in an oxidizing atmosphere tocarbonize the resin.

The carbon fibers are preferably rayon fibers. Alternatively, the carbonfibers can be pitch, PAN or other carbon fibers. Suitable carbon fibersare commercially available from Ashland Petroleum Company, located inAshland, Ky., and from Anshan East Asia Carbon Company, located inAnshan, China.

According to a preferred embodiment, the binder is an organic materialthat can be carbonized by heating, i.e., a carbonizable organicmaterial. The binder is a carbon-bond precursor. For example, the bindercan be pitch, thermosetting resin or phenolic resin. Preferably, thebinder is a phenolic resin, which is water-soluble and provides asuitably high carbon yield when carbonized. The phenolic resin ispreferably in powder form. The carbon fibers and the binder are mixed ina suitable ratio. Preferably, the ratio of the carbon fibers to resin(on a weight basis) is from about 2:1 to about 4:1.

The slurry is formed into a shaped body having the configuration that isdesired for the carbon fiber composite, preferably a cylinder or disc.In a preferred embodiment, slurry is formed into a shaped body by avacuum molding process, such as the process described by George C. Weiand J. M. Robbins, which orients the carbon fibers in a preferreddirection in the body.

According to the embodiment, after vacuum molding, the molded form isdried. The dried form is removed from the mold and cured. The curingprocess cross-links the binder. The curing temperature is selected basedon factors including the binder composition. For example, for a phenolicresin binder, the form is cured in an air or other suitable atmosphereat a preferred temperature of from about 130° C. to about 150° C. Thecured carbon fiber composite has a monolithic structure.

According to the embodiment, the cured carbon fiber composite iscarbonized. In this step, the cured carbon fiber composite is heated ata selected temperature and for an effective amount of time tosufficiently carbonize the binder. For example, the carbon fibercomposite can be heated at a temperature of about 600° C. to about 700°C. in an inert gas atmosphere to carbonize phenolic resin.

The resulting carbonized monolithic carbon fiber composite can bemachined to form one or more cavities at one or more selected locations.The cavities can be formed, e.g., by drilling the monolithic body. Forexample, at least one cavity can extend completely through the body,such as shown in FIG. 1, or alternatively can extend partially throughthe body, such as shown in FIG. 3, so that the body includes an open endand an opposite closed end. As described above, the cavity can extendalong only a portion of the length of the body, such as less than about¼, less than ½, or less than about ¼ of the body length. The covers canbe formed by slicing segments having a suitable length from themonolithic body and machining the segments to form covers of a desiredshape and size.

However, in another preferred embodiment, the resulting carbonizedmonolithic carbon fiber composite does not include a cavity. In suchembodiment, the catalyst material can be incorporated in the body of thecarbon fiber composite during manufacture of the carbon fiber composite,e.g., by including the catalyst in the slurry. Alternatively, catalystmaterial can be impregnated into the body of the carbon fiber compositefollowing manufacture of the carbon fiber composite. In such embodiment,the carbon fiber composite preferably has a disc configuration andpreferably has a length of from about 3 mm to about 20 mm. One or morediscs can be provided in a filter. As described above, a sleeve thatdoes not also contain catalyst can be provided on the outer surface ofthe body.

In a preferred embodiment, the filter component is incorporated in thefilter portion of a smoking article. The filter component can beincorporated in one or more locations in the filter portion. The filtercomponent can also be used in various filter constructions.

In another embodiment, the filter component can be used in combinationwith at least one flavoring-release additive, such as described incommonly-assigned U.S. Application Publication No. 2004/0129280, whichis incorporated herein by reference in its entirety. Theflavoring-release additive can be disposed downstream from the filtercomponent in a cigarette, for example.

The flavoring-release additive can include one or more flavorings, suchas menthol, mint, e.g., peppermint or spearmint, chocolate, licorice,citrus and other fruit flavors, gamma octalactone, vanillin, ethylvanillin, breath freshener flavors, spice flavors, such as cinnamon,methyl salicylate, linalool, bergamot oil, geranium oil, lemon oil,ginger oil and tobacco flavor.

The flavoring is encapsulated by an encapsulating material that protectsthe flavoring from exposure to undesired substances in the cigarette andatmosphere, and substantially prevents the flavoring from being releaseduntil the flavoring-release additive is heated to the flavoring-releasetemperature during smoking of the cigarette. Consequently, the flavoringis preferably substantially prevented from migrating in the cigaretteand from reacting with other substances in the cigarette or with theenvironment.

As described above, exothermic reactions that can be catalyzed by thecatalyst of the filter component, such as the oxidation of CO, evolve alarge amount of heat. In a preferred embodiment, the evolved heat isutilized to heat the flavoring release additive to the flavoring releasetemperature during smoking of a cigarette, thereby releasing theflavoring in the filter downstream from the filter component.

The flavoring-release additive can have different structures andcompositions. In one preferred embodiment, the flavoring-releaseadditive is in the form of beads. The beads preferably encapsulate theflavoring and provide for controlled release of the flavoring in acigarette during puff cycles. The beads preferably comprise at least oneencapsulating material and at least one flavoring. The encapsulatingmaterial preferably comprises a binder, which can be, e.g., one or moreof palm oil, konjac gum, xylitol, zein, hydroxypropylceliulose,sorbitol, maltitol and hydroxypropylmethylcellulose. Depending on thecomposition of the beads, the minimum temperature at which the beadsrelease the flavoring can be adjusted. Beads comprising one or more ofthe above-described binders preferably have a minimum temperature atwhich the flavoring is released of at least about 40° C., such as about40° C. to about 150° C. Cigarettes preferably comprise an amount of thebeads that provides a desired amount of the flavoring in the cigarette.

In another preferred embodiment, the flavoring-release additive includesa film. The film preferably encapsulates the flavoring and enables thecontrolled temperature release of the flavoring in a cigarette duringsmoking. The film-type flavoring-release additive preferably comprisesat least one encapsulating material and at least one flavoring. A filmcomprising one or more of the above-described binders preferably has aminimum temperature at which the flavoring is released of at least about50° C., such as up to about 120° C. Cigarettes preferably comprise anamount of the film that releases a desired amount of the flavoringduring smoking of the cigarette.

In another preferred embodiment, the flavoring-release additive is aninclusion complex. The inclusion complex comprises a “host molecule,”and the flavoring is the “guest molecule” in the inclusion complex. Theinclusion complex provides for controlled release of the flavoring inthe cigarette during smoking. In a preferred embodiment, the flavoringis a lipophilic organic flavoring, which preferably concentrates withina hydrophobic cavity of the host molecule. Suitable flavorings include,but are not limited to, menthol, mint, such as peppermint and spearmint,chocolate, licorice, citrus and other fruit flavors, gamma octalactone,vanillin, ethyl vanillin, breath freshener flavors, spice flavors, suchas cinnamon, methyl salicylate, linalool, bergamot oil, geranium oil,lemon oil, ginger oil and tobacco flavor.

The host molecule of the inclusion complex is preferably a cyclodextrin.More preferably, the inclusion complex comprises beta-cyclodextrin,which can desirably accommodate a wide variety of guest molecules and isreadily available. The minimum temperature at which the inclusioncomplex comprising a cyclodextrin releases the flavoring is preferablyat least about 60° C., such as from about 60° C. to about 125° C.Cigarettes preferably comprise an amount of the inclusion complex thatprovides a desired amount of the flavoring in the cigarette.

FIGS. 23 and 24 illustrate cigarettes 2 including different exemplaryfilter constructions in which the filter component (and an optionalflavoring-release additive) can be incorporated. In each of theseembodiments, more than one filter component can be incorporated in thecigarette filter.

FIG. 23 illustrates a cigarette 2 including a tobacco column 4, a filterportion 6, and a mouthpiece filter plug 8. The filter component can beincorporated, e.g., in place of the folded paper 10, which is disposedin the hollow interior of a free-flow sleeve 12 forming part of thefilter portion 6.

FIG. 24 shows a cigarette 2 including a tobacco column 4 and a filterportion 6 in the form of a plug-space-plug filter including a mouthpiecefilter 8, a plug 16, and a space 18. The plug 16 can comprise a tube orsolid piece of material, such as polypropylene or cellulose acetatefibers. The tobacco column 4 and the filter portion 6 are joinedtogether with tipping paper 14. The filter portion 6 can include afilter overwrap 11. The filter component can be incorporated, e.g., inplace of the plug 16 and/or in the space 18.

In another embodiment, the filter component can be placed in the filterportion of a cigarette for use with an electrical smoking device.“Non-traditional” cigarettes include cigarettes for electrical smokingsystems, such as described in commonly-assigned U.S. Pat. Nos.6,026,820; 5,988,176; 5,915,387; 5,692,526; 5,692,525; 5,666,976 and5,499,636, each of which is incorporated herein by reference in itsentirety.

FIG. 25 illustrates an embodiment of a cigarette 100, which can be usedwith an electrical smoking device. As shown, the cigarette 100 includesa tobacco column 61 and a filter portion 63 joined by tipping paper 65.The filter portion 63 contains a tubular free-flow filter element 102and a mouthpiece filter plug 104. The free-flow filter element 102 andmouthpiece filter plug 104 can be joined together as a combined plug 110with a plug wrap 112. The tobacco column 61 can have various formsincorporating one or more of an overwrap 71, another tubular free-flowfilter element 74, a cylindrical tobacco plug 80 preferably wrapped in aplug wrap 84, a tobacco web 67 comprising a base web 69 and tobaccoflavor material 70, and a void 91. The free-flow filter element 74provides structural definition and support at the tipped end 73 of thetobacco column 61. At the free end 78 of the tobacco column 61, thetobacco web 67 and an overwrap 71 are wrapped about a cylindricaltobacco plug 80. Various modifications can be made to a filterarrangement for such a cigarette incorporating the filter component.

The filter component can be placed at one or more locations of thefilter portion 63 of the cigarette 100. For example, the filtercomponent can replace the tubular free-flow filter element 102, thefree-flow filter element 74 and/or be placed in the void space 91.

In the embodiments of the cigarettes shown in FIGS. 23-25, an optionalflavoring-release additive can be placed downstream from the filtercomponent(s).

An exemplary embodiment of a method of making a filter comprisesincorporating a filter component (and an optional flavoring-releaseadditive) into a cigarette filter. The catalyst can catalyze thechemical reaction of one or more selected components of mainstreamtobacco smoke. Any conventional or modified method of making cigarettefilters may be used to incorporate the filter component in thecigarette.

Embodiments of methods for making cigarettes comprise placing a paperwrapper around a tobacco column, and attaching a cigarette filter to thetobacco column to form the cigarette. The cigarette filter contains thefilter component.

Examples of suitable types of tobacco materials that may be used includeflue-cured, Burley, Md. or Oriental tobaccos, rare or specialty tobaccosand blends thereof. The tobacco material can be in the form of tobaccolamina; processed tobacco materials, such as volume expanded or puffedtobacco, processed tobacco stems, such as cut-rolled or cut-puffedstems, reconstituted tobacco materials, or blends thereof. Tobaccosubstitutes may also be used.

In cigarette manufacture, the tobacco is normally in the form of cutfiller. The cigarettes may further comprise one or more flavorants orother additives (e.g., burn additives, combustion modifying agents,coloring agents, binders and the like).

Known techniques for cigarette manufacture may be used to incorporatethe filter component. The resulting cigarettes can be manufactured toany desired specification using standard or modified cigarette makingtechniques and equipment. The cigarettes may range from about 50 mm toabout 120 mm in length. The circumference is from about 15 mm to about30 mm, and preferably around 25 mm.

Other preferred embodiments provide methods of smoking a cigarettedescribed above. “Smoking” of a cigarette means the heating orcombustion of the cigarette to form tobacco smoke. Generally, smoking ofa cigarette involves lighting one end of the cigarette and drawing thecigarette smoke through the mouth end of the cigarette, while thetobacco contained in the tobacco column undergoes a combustion reaction.Smoke is drawn through the cigarette. During the smoking of thecigarette, the catalyst of the filter component catalyzes the chemicalreaction of one or more selected constituents of mainstream smoke.

However, the cigarette may also be smoked by other means. For example,the cigarette may be smoked by heating the cigarette and/or heatingusing an electrical heater, as described, e.g., in commonly-assignedU.S. Pat. No. 6,053,176; 5,934,289; 5,591,368 or 5,322,075, each ofwhich is incorporated herein by reference in its entirety. In anotherembodiment, the cigarette may include a combustible heat source separatefrom a bed of tobacco, such as described in commonly-assigned U.S. Pat.No. 4,966,171.

While the invention has been described in detail with reference topreferred embodiments thereof, it will be apparent to one skilled in theart that various changes can be made, and equivalents employed, withoutdeparting from the scope of the invention.

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 14. A cigarette filter, comprising: a filter component including: a porous, carbon-bonded carbon fiber composite; and a catalyst contained in the composite, the catalyst being effective to catalyze the chemical reaction of at least one selected constituent of mainstream tobacco smoke in the cigarette filter wherein the carbon fiber composite has a disc configuration without a cavity and the catalyst is dispersed throughout the disc.
 15. The cigarette filter of claim 14, further comprising a thermally insulate sleeve surrounding the disc, the sleeve not containing the catalyst.
 16. The cigarette filter of claim 14, wherein the catalyst comprises nanoscale-sized particles.
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 23. A cigarette, comprising: a cigarette filter according to claim 14, and a tobacco column attached to the cigarette filter.
 24. The cigarette of claim 23, which is an electrically heated cigarette or a cigarette including a combustible fuel element.
 25. The cigarette of claim 23, including a flavoring-release additive downstream from the filter component in the cigarette filter, the flavoring-release additive including at least one flavoring which is releasable in the cigarette when the flavoring-release additive is heated to at least a minimum temperature in the cigarette.
 26. The cigarette of claim 25, wherein the catalyst is effective to catalyze at least the oxidation the CO, and sufficient heat is evolved during the oxidation of the CO to heat the flavoring-release additive to at least the minimum temperature such that the at least one flavoring is released in the cigarette.
 27. The cigarette of claim 23, wherein the catalyst comprises nanoscale-sized particles.
 28. (canceled)
 29. A method of manufacturing a cigarette filter, comprising incorporating at least one filter component according to claim 14 in a filter.
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 31. A method of manufacturing a cigarette, comprising: placing a paper wrapper around a tobacco column; and attaching the cigarette filter according to claim 14 to the tobacco column to form the cigarette.
 32. (canceled)
 33. A method of treating mainstream tobacco smoke, comprising heating or lighting the cigarette according to claim 23 to form smoke and drawing the smoke through the cigarette, the catalyst catalyzing the chemical reaction of at least one gaseous constituent included in the smoke. 